package com.mongo.morphia.complex.common;



import java.util.prefs.Preferences;

/**
 * Static methods for translating Base64 encoded strings to byte arrays
 * and vice-versa.
 *
 * @author  Josh Bloch
 * @version 1.4, 01/23/03
 * @see     Preferences
 * @since   1.4
 */
public class Base64Encoder {
	/**
	 * Translates the specified byte array into a Base64 string as per
	 * Preferences.put(byte[]).
	 */
	public static String byteArrayToBase64(byte[] a) {
		return byteArrayToBase64(a, false);
	}

	/**
	 * Translates the specified byte array into an "aternate representation"
	 * Base64 string.  This non-standard variant uses an alphabet that does
	 * not contain the uppercase alphabetic characters, which makes it
	 * suitable for use in situations where case-folding occurs.
	 */
	public static String byteArrayToAltBase64(byte[] a) {
		return byteArrayToBase64(a, true);
	}

	private static String byteArrayToBase64(byte[] a, boolean alternate) {
		int aLen = a.length;
		int numFullGroups = aLen/3;
		int numBytesInPartialGroup = aLen - 3*numFullGroups;
		int resultLen = 4*((aLen + 2)/3);
		StringBuffer result = new StringBuffer(resultLen);
		char[] intToAlpha = (alternate ? intToAltBase64 : intToBase64);

		// Translate all full groups from byte array elements to Base64
		int inCursor = 0;
		for (int i=0; i<numFullGroups; i++) {
			int byte0 = a[inCursor++] & 0xff;
			int byte1 = a[inCursor++] & 0xff;
			int byte2 = a[inCursor++] & 0xff;
			result.append(intToAlpha[byte0 >> 2]);
			result.append(intToAlpha[(byte0 << 4)&0x3f | (byte1 >> 4)]);
			result.append(intToAlpha[(byte1 << 2)&0x3f | (byte2 >> 6)]);
			result.append(intToAlpha[byte2 & 0x3f]);
		}

		// Translate partial group if present
		if (numBytesInPartialGroup != 0) {
			int byte0 = a[inCursor++] & 0xff;
			result.append(intToAlpha[byte0 >> 2]);
			if (numBytesInPartialGroup == 1) {
				result.append(intToAlpha[(byte0 << 4) & 0x3f]);
				result.append("==");
			} else {
				// assert numBytesInPartialGroup == 2;
				int byte1 = a[inCursor++] & 0xff;
				result.append(intToAlpha[(byte0 << 4)&0x3f | (byte1 >> 4)]);
				result.append(intToAlpha[(byte1 << 2)&0x3f]);
				result.append('=');
			}
		}
		// assert inCursor == a.length;
		// assert result.length() == resultLen;
		return result.toString();
	}

	/**
	 * This array is a lookup table that translates 6-bit positive integer
	 * index values into their "Base64 Alphabet" equivalents as specified 
	 * in Table 1 of RFC 2045.
	 */
	private static final char intToBase64[] = {
		'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
		'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
		'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
		'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
		'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/'
	};

	/**
	 * This array is a lookup table that translates 6-bit positive integer
	 * index values into their "Alternate Base64 Alphabet" equivalents.
	 * This is NOT the real Base64 Alphabet as per in Table 1 of RFC 2045.
	 * This alternate alphabet does not use the capital letters.  It is
	 * designed for use in environments where "case folding" occurs.
	 */
	private static final char intToAltBase64[] = {
		'!', '"', '#', '$', '%', '&', '\'', '(', ')', ',', '-', '.', ':',
		';', '<', '>', '@', '[', ']', '^',  '`', '_', '{', '|', '}', '~',
		'a', 'b', 'c', 'd', 'e', 'f', 'g',  'h', 'i', 'j', 'k', 'l', 'm',
		'n', 'o', 'p', 'q', 'r', 's', 't',  'u', 'v', 'w', 'x', 'y', 'z',
		'0', '1', '2', '3', '4', '5', '6',  '7', '8', '9', '+', '?'
	};

	/**
	 * Translates the specified Base64 string (as per Preferences.get(byte[]))
	 * into a byte array.
	 * 
	 * @throw IllegalArgumentException if <tt>s</tt> is not a valid Base64
	 *        string.
	 */
	public static byte[] base64ToByteArray(String s) {
		return base64ToByteArray(s, false);
	}

	/**
	 * Translates the specified "aternate representation" Base64 string
	 * into a byte array.
	 * 
	 * @throw IllegalArgumentException or ArrayOutOfBoundsException
	 *        if <tt>s</tt> is not a valid alternate representation
	 *        Base64 string.
	 */
	public static byte[] altBase64ToByteArray(String s) {
		return base64ToByteArray(s, true);
	}

	private static byte[] base64ToByteArray(String s, boolean alternate) {
		byte[] alphaToInt = (alternate ?  altBase64ToInt : base64ToInt);
		int sLen = s.length();
		int numGroups = sLen/4;
		if (4*numGroups != sLen)
			throw new IllegalArgumentException(
				"String length must be a multiple of four.");
		int missingBytesInLastGroup = 0;
		int numFullGroups = numGroups;
		if (sLen != 0) {
			if (s.charAt(sLen-1) == '=') {
				missingBytesInLastGroup++;
				numFullGroups--;
			}
			if (s.charAt(sLen-2) == '=')
				missingBytesInLastGroup++;
		}
		byte[] result = new byte[3*numGroups - missingBytesInLastGroup];

		// Translate all full groups from base64 to byte array elements
		int inCursor = 0, outCursor = 0;
		for (int i=0; i<numFullGroups; i++) {
			int ch0 = base64toInt(s.charAt(inCursor++), alphaToInt);
			int ch1 = base64toInt(s.charAt(inCursor++), alphaToInt);
			int ch2 = base64toInt(s.charAt(inCursor++), alphaToInt);
			int ch3 = base64toInt(s.charAt(inCursor++), alphaToInt);
			result[outCursor++] = (byte) ((ch0 << 2) | (ch1 >> 4));
			result[outCursor++] = (byte) ((ch1 << 4) | (ch2 >> 2));
			result[outCursor++] = (byte) ((ch2 << 6) | ch3);
		}

		// Translate partial group, if present
		if (missingBytesInLastGroup != 0) {
			int ch0 = base64toInt(s.charAt(inCursor++), alphaToInt);
			int ch1 = base64toInt(s.charAt(inCursor++), alphaToInt);
			result[outCursor++] = (byte) ((ch0 << 2) | (ch1 >> 4));

			if (missingBytesInLastGroup == 1) {
				int ch2 = base64toInt(s.charAt(inCursor++), alphaToInt);
				result[outCursor++] = (byte) ((ch1 << 4) | (ch2 >> 2));
			}
		}
		// assert inCursor == s.length()-missingBytesInLastGroup;
		// assert outCursor == result.length;
		return result;
	}

	/**
	 * Translates the specified character, which is assumed to be in the
	 * "Base 64 Alphabet" into its equivalent 6-bit positive integer.
	 *
	 * @throw IllegalArgumentException or ArrayOutOfBoundsException if
	 *        c is not in the Base64 Alphabet.
	 */
	private static int base64toInt(char c, byte[] alphaToInt) {
		int result = alphaToInt[c];
		if (result < 0)
			throw new IllegalArgumentException("Illegal character " + c);
		return result;
	}

	/**
	 * This array is a lookup table that translates unicode characters
	 * drawn from the "Base64 Alphabet" (as specified in Table 1 of RFC 2045)
	 * into their 6-bit positive integer equivalents.  Characters that
	 * are not in the Base64 alphabet but fall within the bounds of the
	 * array are translated to -1.
	 */
	private static final byte base64ToInt[] = {
		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
		-1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54,
		55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4,
		5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23,
		24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34,
		35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51
	};

	/**
	 * This array is the analogue of base64ToInt, but for the nonstandard
	 * variant that avoids the use of uppercase alphabetic characters.
	 */
	private static final byte altBase64ToInt[] = {
		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 0, 1,
		2, 3, 4, 5, 6, 7, 8, -1, 62, 9, 10, 11, -1 , 52, 53, 54, 55, 56, 57,
		58, 59, 60, 61, 12, 13, 14, -1, 15, 63, 16, -1, -1, -1, -1, -1, -1,
		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
		-1, -1, -1, 17, -1, 18, 19, 21, 20, 26, 27, 28, 29, 30, 31, 32, 33,
		34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50,
		51, 22, 23, 24, 25
	};
    
	public static void main(String args[]) {
		int numRuns  = Integer.parseInt(args[0]);
		int numBytes = Integer.parseInt(args[1]);
		java.util.Random rnd = new java.util.Random();
		for (int i=0; i<numRuns; i++) {
			for (int j=0; j<numBytes; j++) {
				byte[] arr = new byte[j];
				for (int k=0; k<j; k++)
					arr[k] = (byte)rnd.nextInt();

				String s = byteArrayToBase64(arr);
				byte [] b = base64ToByteArray(s);
				if (!java.util.Arrays.equals(arr, b))
					System.out.println("Dismal failure!");

				s = byteArrayToAltBase64(arr);
				b = altBase64ToByteArray(s);
				if (!java.util.Arrays.equals(arr, b))
					System.out.println("Alternate dismal failure!");
			}
		}
	}
}
